This document discusses coronary artery calcium (CAC) scoring, which is a noninvasive imaging technique used to assess risk of coronary heart disease. It begins by introducing CAC and its role in atherosclerosis. It then covers various CAC scoring methods and discusses interpreting absolute versus percentile scores. The document also addresses pitfalls in CAC scoring and how it can be used to guide statin and aspirin therapy. It concludes by covering special considerations for CAC scoring in patients with chronic kidney disease, diabetes, different age groups, and very high CAC scores.
2. INTRODUCTION
Coronary heart disease (CHD) remains a leading cause of death worldwide,
accounting for 16% of total deaths globally
3. Pathophysiology
Atherosclerosis plays a central role, with early fatty streaks progressing to late
complex atheromas
Vascular calcification, the pathogenic and process of ectopic bone production,
specifically was shown to strongly correlate with degree of atherosclerosis (both
calcified and noncalcified)
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5. Vascular calcification was shown independently to predict cardiovascular
morbidity and mortality
These associations, combined with the radio-opaque appearance of calcium
hydroxyappatite on CT images, have led to extensive investigation of the
quantification, or scoring, of coronary artery calcium (CAC).
CAC scoring has emerged as a widely available and powerful tool for
stratifying cardiovascular risk, predicting patient outcomes, and guiding
preventive therapy
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8. CAC Scoring methods
Agatston score
Volume score
Mass score
Agatston method is the most validated and widely used in practice, thereby
serving as the reference standard
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16. Absolute versus Percentile CAC Scoring
CAC is typically quantified using the Agatston score
The Agatston score can be reported as an absolute score (in Agatston units) or
as an age-, sex-, and race-specific percentile that is derived using the MESA
risk score calculator
The absolute score is the best predictor of the total risk of a CHD event for an
individual in the near to midterm (in the next 5 to 10 years)
In contrast, the percentile score best represents relative risk of CHD event for
the individual compared with other individuals of the same age, race, and sex
In this way, the percentile score is the better predictor of lifetime risk of
developing CHD.
19. Respiratory Motion Artifacts
With regard to image acquisition, respiratory motion artifacts are a common
problem that can hinder image quality
Technologists should take precaution of this and ensure that proper breathing
instructions are relayed to the patient before the initiation of scanning
20. Electrocardiographic Gating
Can arise during image acquisition owing to patient
factors such as arrhythmias and/or technical factors
such as static in ECG leads
21. Technical Issues
Partial exclusion of coronary arteries from the field of
view can sometimes occur
Can be avoided by educating the technologist
regarding careful planning of image boundaries from
the topogram
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23. Calcium score calculation- artifacts
Potential pitfalls that can confound calcium score
calculations include:
Coronary artery motion artifacts
Non coronary calcifications
Streak artifacts from adjacent metallic prostheses
Inclusion of patients who have undergone coronary artery
stent placement or coronary artery bypass graft
placement
27. The 10-year ASCVD risk is combined with the CAC score to guide primary
prevention with statins
The current recommendation is to incorporate the CAC score as a decision-
making tool to reclassify risk and guide statin therapy in patients older than 40
years who have borderline to intermediate (5%–20%) 10- year ASCVD risk
For patients with a risk of less than 5%, statin treatment is not recommended;
as an exception, statin treatment may be recommended for select patients in this
group with risk factors and a strong CAD family history
For patients with a greater than 20% risk, statin treatment is recommended
regardless of the CAC score
35. Aspirin is beneficial for CAC = 0, only if patients have >20% ASCVD risk
Regardless of CAC score, aspirin is net harmful in those with <5% risk or
with increased bleeding risk
AHA guidelines, which now recommend consideration of aspirin therapy
for all individuals with CAC >100
38. CHRONIC KIDNEY DISEASE
In CKD pts, a significantly more pronounced, disseminated, and fast-
progressing calcification of the vascular system (includes the coronary arteries)
Coronary artery calcification develops early after the onset of CKD and is
closely a/w mineral and bone disorders, which include but are not limited to
secondary hyperparathyroidism
Factors such as inflammation and obesity, commonly seen in CKD, lead to the
acceleration of atherosclerotic plaques in the arteries
39. The ESC adds that active management instead of risk assessment by CAC is of
more vital importance for CKD pts
The ACC/AHA note that CKD is already a risk enhancer. If there is still
uncertainty regarding risk estimate, American guidelines allow for reclassifying
up or down with CAC
40. DIABETES MELLITUS
Individuals with diabetes present with a risk for CV events comparable to those
for patients with an actual ASCVD history
the presence of any CAC in individuals with DM equates with a higher risk of
all-cause mortality, and CAC scoring becomes of vital importance as a risk
stratifier
41. The ESC guidelines: young patients (T1DM <35 yrs of age, T2 DM <50 yrs),
with DM duration <10 years and without other risk factors, are considered at low-
moderate risk for ASCVD
Within this patient segment, European guidelines suggest that individuals may
benefit from CAC scoring to up- or down-classify their level of risk standing
42. ACC/AHA and denotes that intermediate risk factors, including impaired fasting
glucose (in men at or older than 50 years of age and women at or older than 60
years of age) along with a risk modifier of CAC >0, favor the use of statins
43. CAC AMONG OLDER AGE GROUPS
For individuals >75 years of age, guidelines worldwide acknowledge the utility
of CAC in reclassifying CV risk and predicting CV mortality
ACC/AHA guidelines state that for adults 76 to 80 years of age
with an LDL-C level of 70 to 189 mg/dL, CAC of 0 warrants the
deferral of statin therapy
44. CAC AMONG YOUNGER AGE GROUPS
For low-risk individuals under 45 years of age, the ACC/AHA use CAC scoring
more sparingly
They reserve this screening instead for younger patients with increased risk
factors
the ACC/AHA recommends that ASCVD risk factors be evaluated every 4 to 6
years and that CAC scoring be performed if there are risk factors including
history of hyperglycemia, hyperlipidemia, hypertension, or smoking
47. In patients with a CAC score of 0 on the index scan
Consider recommending repeat CAC testing in 5–7 years for low-risk
individuals
3–5 years for intermediate-risk individuals
Approximately 3 years for high-risk individuals or those with diabetes
48.
49. New CAC Score Group: CAC of Greater than 1000
CAC scores of greater than 300 or greater than 400 have been traditionally
recognized as the highest risk classification of CAC
There are a unique group of individuals with CAC scores of greater than 1000,
many of whom are asymptomatic at the time of scanning
high CAC values are heavily influenced by CAC density, which may be a/ w more
favorable prognosis, as denser CAC are more indicative of stable plaques, which
are less prone to rupture
50. very high CAC scores of greater than 1000 was found to have greater CAC
area and more extra-coronary calcium, and a/w higher risk of CVD, CHD,
cancer, and all-cause mortality than those with CAC scores of 400–999
These patients have found to have as much risk as those in secondary prevention
( prior MI ) suggesting that even more aggressive management of modifiable
risk factors might be warranted in this subgroup of individuals
51. CAC scores of greater than 1000 should be
considered a distinct very high-risk group and
should be identified as such on score reports
Recommendation
s
52. CAC Distribution within the Coronary Arteries
Another consideration when scoring and reporting CAC is the CAC distribution
within the coronary tree
For a given absolute CAC score, compared with single vessel CAC, CAC in
multiple vessels is associated with higher risk of mortality
In limited circumstances it is important to note the vessel affected, as CAC
involving the left main was a/w increased mortality risk
53. the Agatston score does not factor in the distribution of CAC, like the calcium
coverage score, take CAC distribution into consideration but are less
reproducible and require much longer reading time than the Agatston score,
limiting their incremental value
Currently, a simple expression of the number of coronary arteries with CAC and
whether there is CAC in the left main is sufficient to enhance risk discrimination
54. When reporting CAC scores, the number of coronary arteries with
CAC should be noted within the report (0–4, including the left
main)
Presence of left main CAC should also be noted in the study
conclusions.
Recommendation
s
59. Take Home Messages
When to consider CAC testing?
In intermediate-risk or selected borderline-risk adults, if the decision about statin
use remains uncertain, it is reasonable to use a CAC score in the decision to
withhold, postpone or initiate statin therapy.
Emphasis on "power of zero:" use of CAC testing to
identify low risk patients
As opposed to risk enhancers and screening tools that may be used to identify
higher risk patients, CAC testing is now mostly used for identifying lower risk
patients among those who would otherwise be candidates for statin therapy but
who have a preference to avoid such therapy.
60. CAC may also be useful in older individuals
The new guideline also supports the utility of CAC measurement in
identifying the absence of atherosclerotic plaque in older adults
Specifically, the guideline states that in adults 76 to 80 years of age with an
LDL-C level of 70 to 189 mg/dL, it may be reasonable to measure CAC to
reclassify those with a CAC score of zero to avoid statin therapy.
61. Must interpret CAC test results in context of overall
patient risk
A CAC score of zero can be helpful in reclassifying risk to a lower risk
group
However, a score of zero does not imply zero risk, and the results of the
test should always be incorporated with other known risk factors
It is for this reason that CAC testing is not recommended in high risk
patients (i.e., 10-year ASCVD risk ≥20%), and that at times clinicians and
patients may elect to initiate statin therapy despite a CAC of zero.
